Cancer is a major devastating disease, and is a leading cause of death worldwide. Despite the progress in cancer treatment, cancer mortality rate remains high. Therefore, the discovery and development of improved anticancer drugs to treat cancer are needed. 4H-chromenes have strong cytotoxicity against a panel of human cancer cell lines involving pathways that include microtubule depolarization and tumor vasculature disruption. A chromene analog, Crolibulin™ (EPC2407) is currently in Phase I/II clinical trials for the treatment of advanced solid tumors. This article reviews the general synthesis, biological activities and structure-activity relatinships of different classes of chromenes.